---
id: CVE-2026-28699
title: >-
  Gitea: OAuth2 access token scope enforcement bypass via HTTP Basic
  authentication
summary: >-
  Gitea: OAuth2 access token scope enforcement bypass via HTTP Basic
  authentication
severity: high
cvss: 8.1
cwe:
  - CWE-284
  - CWE-863
vendor: gitea
product: code.gitea.io/gitea
ecosystem: go
affected:
  - code.gitea.io/gitea <= 1.26.1
patched:
  - code.gitea.io/gitea 1.26.2
published: '2026-06-16'
updated: '2026-06-16'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-9r5x-wg6m-x2rc'
references:
  - url: 'https://github.com/go-gitea/gitea/security/advisories/GHSA-9r5x-wg6m-x2rc'
  - url: 'https://github.com/advisories/GHSA-9r5x-wg6m-x2rc'
tags:
  - ghsa
  - go
  - exploit-available
ingestedAt: '2026-06-29T14:31:47.459Z'
epss: 0.00551
epssPercentile: 0.43647
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/Alardiians/gitea-CVE-2026-28699'
  checkedAt: '2026-09-25T08:20:54.217Z'
exploitAvailable: true
---

## Overview

### Summary

Gitea fails to enforce OAuth2 access token scopes when the token is submitted via HTTP Basic authentication instead of a Bearer token. An OAuth2 application granted only `read:user` can use the same token as `Authorization: Basic base64(<token>:x-oauth-basic)` and perform write actions, including modifying profiles, adding email addresses, creating repositories, and deleting repositories as the authorizing user.

### Details

**Root cause:** `services/auth/basic.go` accepts OAuth2 access tokens through the Basic auth path but does not store the token scope in the request context:

```go
// services/auth/basic.go
if uid != 0 {
    store.GetData()["LoginMethod"] = OAuth2TokenMethodName
    store.GetData()["IsApiToken"] = true   // scope is NOT set
    return u, nil
}
```

The scope enforcement middleware in `routers/api/v1/api.go` exits early when `ApiTokenScope` is absent:

```go
// routers/api/v1/api.go — tokenRequiresScopes
scope, scopeExists := ctx.Data["ApiTokenScope"].(auth_model.AccessTokenScope)
if ctx.Data["IsApiToken"] != true || !scopeExists {
    return   //<- exits without checking scope, all actions permitted
}
```

When a token arrives via Bearer, `ApiTokenScope` is populated and scope checks apply normally. When the same token arrives via Basic auth, `ApiTokenScope` is never set, so `tokenRequiresScopes` returns immediately and no scope is enforced.

**Suggested fix:** When an OAuth2 access token is accepted in `services/auth/basic.go`, populate `ApiTokenScope` in the request context identically to the Bearer-token OAuth2 path.

### PoC

1. Create an OAuth2 application in Gitea.
2. Authorize it as a normal user with scope `read:user` only.
3. Take the resulting access token and call a write endpoint both ways:

**Bearer | correctly blocked:**
```
Authorization: Bearer <token>
PATCH /api/v1/user/settings  ->  403 Forbidden
```

**Basic | bypass:**
```
Authorization: Basic base64(<token>:x-oauth-basic)
PATCH /api/v1/user/settings  ->  200 OK
```

**All verified bypass endpoints using a `read:user`-only token:**

| Endpoint | Bearer | Basic |
|---|---|---|
| `PATCH /api/v1/user/settings` | 403 | 200 |
| `POST /api/v1/user/emails` | 403 | 200 |
| `POST /api/v1/user/repos` | 403 | 200 |
| `PATCH /api/v1/repos/{owner}/{repo}` | 403 | 200 |
| `DELETE /api/v1/repos/{owner}/{repo}` | 403 | 200 |

The bypass respects the user's normal repository permissions, it does not grant access to repositories the user cannot otherwise reach, and does not escalate to admin.

### Impact

Any OAuth2 application with any restricted scope can silently operate beyond its granted permissions by switching from Bearer to Basic auth. An attacker who obtains a token (e.g. via a malicious OAuth2 app a user authorized) can:

- Modify the victim's profile and settings
- Add attacker-controlled email addresses to the victim's account
- Create repositories as the victim
- Modify or delete the victim's private repositories

The entire OAuth2 scope system is effectively bypassed for any token submitted via Basic auth.

## Affected packages

- `code.gitea.io/gitea <= 1.26.1`

## Remediation

Upgrade to a patched release:

- `code.gitea.io/gitea 1.26.2`